Histamine is a multifunctional chemical transmitter that signals through cell surface receptors that are linked to intracellular pathways via guanine nucleotide binding proteins. This class of cell surface receptors are called G-protein coupled receptors or GPCRs. There are currently three subtypes of histamine receptors that have been defined pharmacologically and have been divided into H1, H2, and H3 classifications (Hill, et al. 1997). The H1 histamine receptor has been cloned (Yamashita, et al. 1991)and is the target of drugs such as diphenhydramine to block the effects of histamine in allergic responses. The H2 histamine receptor has been cloned (Gantz et al. 1991) and is the target of drugs such as ranitidine to block the effects of histamine on acid secretion in the stomach. The third subtype of histamine receptor was hypothesized to exist in 1983 (Arrang, et al. 1983). It is believed to function as a presynaptic autoreceptor in histamine containing neurons in the central nervous system and as a presynaptic heteroreceptor in non-histamine containing neurons. One of the functions of the H3 receptor is to regulate neurotransmitter release at the presynaptic site. Histamine H3 receptors are thus expressed in the central nervous system, but have also been pharmacologically identified in heart, lung, and stomach, and have been hypothesized to exist in other tissues.
The present invention relates to the isolation and characterization of a human cDNA encoding a histamine H3 receptor and the uses thereof.
A DNA molecule encoding a human histamine H3 receptor has been cloned and characterized and it represents a novel member of the class of receptors that couple to G-proteins. Using a recombinant expression system functional DNA molecules encoding the human histamine H3 receptor have been isolated. The biological and structural properties of these proteins are disclosed, as is the amino acid and nucleotide sequence. The recombinant protein is useful for a variety of purposes, including but not limited to identifying modulators of the human histamine H3 receptor. Modulators identified in the assays disclosed herein are useful, for example, as therapeutic agents, and diagnostic agents. Indications for said therapeutic agents include, but are not limited to, central nervous system disorders, for example depression, anxiety, psychoses (for example schizophrenia), tardive dyskinesia, Parkinson""s disease, obesity, hypertension, Tourette""s syndrome, sexual dysfunction, drug addiction, drug abuse, cognitive disorders, Alzheimer""s disease, senile dementia, obsessive-compulsive behavior, panic attacks, pain, social phobias, eating disorders and anorexia, cardiovascular and cerebrovascular disorders, non-insulin dependent diabetes mellitus, hyperglycemia, constipation, arrhythmia, disorders of the neuroendrocrine system, stress, and spasticity, as well as acid secretin, ulcers, airway constriction, asthma, allergy, inflammation, and prostate dysfunction. The recombinant DNA molecules, and portions thereof, are useful for isolating homologues of the DNA molecules, identifying and isolating genomic equivalents of the DNA molecules, and identifying, detecting or isolating mutant forms of the DNA molecules.